The invention relates generally to contact lenses.
Methods for making silicone elastomer-containing articles such as, for instance, contact lenses, hydrophilic are disclosed in applicants' prior applications Serial Nos. 318,853 and 517,096 which are commonly owned with the present application. With respect to the treatment of contact lenses, these methods basically involve subjecting the surfaces of a contact lens which contains or consists of a silicone elastomer to bombardment with charged particles, particularly ions, using a glow discharge. Application Ser. No. 517,096 is now U.S. Pat. No. 3,959,105 the disclosure of which is incorporated by reference herein.
In order to achieve optimum compatibility between such a silicone elastomer-containing contact lens and the user of the lens, the latter should be seated on the eye in such a manner that it can readily move on the eye. This is necessary since otherwise the edges of the lens may produce impressions in the eye by virtue of too firm a seating of the lens on the eye. The formation of such impressions in the eye is undesirable on physiological grounds. On the other hand, experiments have shown that the sliding of the lens on the cornea of the eye may cause a foreign body sensation to be produced when the concave side of the lens facing the cornea, and which side has been treated in accordance with applicants' above-referenced prior applications, is too strongly hydrophilic.
The same general considerations apply also to conventional contact lenses, that is, contact lenses which do not contain a silicone elastomer. Such contact lenses may also be made hydrophilic, for example, by chemical means such as disclosed in the German publication DT-OS 22 28 528 (corresponding to the U.S. application Serial No. 152,076 in the name of A. E. Barkdoll filed Nov. 16, 1971).
In addition to the above considerations, it must be taken into account that an important reason for providing a contact lens with a hydrophilic surface is to prevent soiling thereof by fatty substances liberated from the eyes. Thus, these substances, which are conveyed to the surface of the lens by the tear fluid, accumulate very rapidly on hydrophobic surfaces and will cause the lens, which is itself clear as glass, to become cloudy or opaque if the surface of the lens is hydrophobic.
The prior art has been unable to provide a contact lens which is capable of satisfactorily meeting the above requirements, that is, a contact lens which can readily move on the eye, which does not produce a foreign body sensation and which yet is not easily soiled. It is clear, therefore, that improvements in the state of the art are desirable.